Looks

looks

Optional.

This section defines a list of “looks”. A look is a color transform defined similarly to a colorspace, with a few important differences.

For example, a look could be defined for a “first pass DI beauty grade”, which is used to view shots with a rough approximation of the final grade.

When the look is defined in the config, you must specify a name, the color transform, and the colorspace in which the grade is performed (the “process space”). You can optionally specify an inverse transform for when the look transform is not trivially invertable (e.g. it applies a 3D LUT)

When an application applies a look, OCIO ensures the grade is applied in the correct colorspace (by converting from the input colorspace to the process space, applies the look’s transform, and converts the image to the output colorspace)

Here is a simple looks: section, which defines two looks:

looks:
  - !<Look>
    name: beauty
    process_space: lnf
    transform: !<CDLTransform> {slope: [1, 2, 1]}

  - !<Look>
    name: neutral
    process_space: lg10
    transform: !<FileTransform> {src: 'neutral-${SHOT}-${SEQ}.csp', interpolation: linear }
    inverse_transform: !<FileTransform> {src: 'neutral-${SHOT}-${SEQ}-reverse.csp', interpolation: linear }

Here, the “beauty” look applies a simple, static ASC CDL grade, making the image very green (for some artistic reason!). The beauty look is applied in the scene-linear lnf colorspace (this colorspace is defined elsewhere in the config.

Next is a definition for a “neutral” look, which applies a shot-specific CSP LUT, dynamically finding the correct LUT based on the SEQ and SHOT context variables.

For example if SEQ=ab and SHOT=1234, this look will search for a LUT named neutral-ab-1234.csp in locations specified in search_path.

The process_space here is lg10. This means when the look is applied, OCIO will perform the following steps:

• Transform the image from it’s current colorspace to the lg10 process space

• Apply apply the FileTransform (which applies the grade LUT)

• Transform the graded image from the process space to the output colorspace

The “beauty” look specifies the optional inverse_transform, because in this example the neutral CSP files contain a 3D LUT. For many transforms, OCIO will automatically calculate the inverse transform (as with the “beauty” look), however with a 3D LUT the inverse transform needs to be defined.

If the look was applied in reverse, and inverse_transform as not specified, then OCIO would give a helpful error message. This is commonly done for non-invertable looks

As in colorspace definitions, the transform can be specified as a series of transforms using the GroupTransform, for example:

looks:
  - !<Look>
    name: beauty
    process_space: lnf
    transform: !<GroupTransform>
      children:
        - !<CDLTransform> {slope: [1, 2, 1]}
        - !<FileTransform> {src: beauty.spi1d, interpolation: nearest}